1. Field of the Invention
The present invention relates generally to the fields of transcriptional regulation. More specifically, the present invention relates to inhibition of binding of hox and homeodomain-containing proteins and uses thereof.
2. Description of the Related Art
The bone morphogenetic proteins (BMPs), a subfamily of TGF.beta., are potent growth factors that regulate embryonic development, vertebral patterning and mesenchymal cell differentiation (1, 2). BMP-2/4, identified as bone inductive growth factors, are important signaling molecules during development of the skeleton in vertebrates (1, 3, 4). Central to the bone morphogenetic protein signaling pathway is the Smad1 protein, which translocates into the nucleus to regulate gene transcription upon direct phosphorylation by bone morphogenetic protein receptors (5-7).
Growth factors in the TGF.beta. superfamily have been implicated in various processes during vertebrate embryonic development. The TGF.beta. action on induction and patterning of mesoderm and skeletal development has been studied intensely. In particular, the TGF.beta. related molecules, BMP-2/4 induces skeletal patterning, growth of limb buds and skeletal cell differentiation. Hox and homeodomain containing transcription factors are also involved in the same process, and have been suggested as a downstream regulation of BMP-4 to mediate its effects. However, there has been little progress in understanding how hox proteins function in embryonic development. Although hox proteins are DNA binding proteins, very little is known about their natural DNA response elements and their role in transcription.
In vertebrates, there are 39 Hox homeobox-containing transcription factor genes, organized into four separate chromosome clusters, which play critical roles in the process and patterning of vertebrate embryonic development (8,18). These 39 genes are subdivided into 13 paralogous groups on the basis of duplication of an ancestral homeobox cluster during evolution, sequence similarity and position within the cluster (9). Each paralog group has been demonstrated to be responsible for morphogenesis of a particular embryonic domain or structure (8). There are three members in Hox paralog group VIII, Hoxb-8, Hoxc-8 and Hoxd-8 (9). Hox genes are required during vertebrate limb bud development, and particularly, Hoxb-8 was suggested to be a transcription factor involved in activating the Sonic hedgehog gene, which is the key mediator in limb development (10,11). Furthermore, Northern blot analysis shows that Hoxc-8 is expressed during human embryo development at high levels in spinal cord, backbone and limbs and at a lower level in heart (12). BMP-2/4 activates expression of Hox genes, induces osteoblast differentiation and controls patterning across the anteroposterior (a-p) axis of developing limb (13).
The prior art is deficient in methods for stimulating osteoblast differentiation and bone formation. The prior art is also deficient in methods of regulating transcription via the Hox proteins and/or homeobox-containing proteins. The present invention fulfills this long-standing need and desire in the art.